One of the most pressing needs in clinical oncology today is for a system which will allow selection of the most effective chemotherapeutic agent against an individiual patient's tumor. The human tumor cloning system is such a system which has the potential for predicting which drug will or will not work against a particular patient's tumor. Despite considerable experience with conventional two layer soft agar system currently utilized to clone human tumors, there are still a variety of problems which plague the system. Chief problems with the two layer soft agar system include inability to grow th majority of patients tumors, low plating efficiencies, the need for very large numbers of tumor cells, tremendous technical time and expense for plating and counting, and the lack of flexibility of the system for utilizing different drug schecules or combinations of drugs. In this renewal application, we propose to develop a new system called the perfused capillary clonging system which has the potential for solving most of these problems. The system is based on the fact that cells growing in a smaller vessel (i.e., a capillary tube) have a higher cloning efficiency than cells growing in 35 mm petri dishes. Thus these capillaries encourage higher plating efficiencies, require fewer cells, have higher percentages of tumors that grow, and require less time and materials for preparation and counting. Also important to the system are the use of special pourous capillary tubes (with a variety of pore sizes available) which can be inserted into a tube and perfused with media containing drugs (single agents or combinations). This perfusion system allows total flexibility for drug scheduling and in vitro combination chemotherapy studies. Overall, this new perfused capillary cloning system should make cloning of human tumors a far more useful and practival tool for drug sensitivity testing as well as for study of human tumor biology.